Pressure loaded gear pump



May 17, 1949, J. A. LAUCK 2,470,355

' PRESSURE-LOADED GEAR PUMP Filed Nov. 23. 1945 jjj \\\\\\\\\\\\\\\\\\\\\\\)gfJ3 Patented Mey 17, 1949 v 2,470,355 PRESSURE LOADED GEAR PUMP John A. Lauck, Shaker Heights, Ohio, assignor,

mesne assignments, to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Application November 2s, 1945, serial No. 630.411

7 Claims. 1

The present invention relates to rotary flui displacement devices of the type having fluid pressure actuated bearing and pumping seals, such devices being generally referred toas pres'- sure loaded pumps.

I have found that in a pressure loaded gear pump of the type embodying axially extending tubular bearing insert portions for the gear journals and radially extending annular plate portions arranged for pressure loading, on at least one side of the gears, serious difficulty is encountered in effecting the required precise over-balance of the annular plate in the direction of the corresponding side face. This is due to the unavoidable radial thickness dimension of the wall ci the tubular portion. In Roth and Lauck copending application Serial No. 439,030, now Patent No. 2,420,622, there is disclosed an example of the form of pressure loaded bushing or liner structure in extensive use prior to the invention of the present arrangement. 'I'his prior construction does notrincorporate a completely enclosing wear-resistant lliner assembly, but on the contrary the gear teeth have the same radial dimension as the annular plate portions, the radial periphery of the teeth cooperating with the main housing wall in pumping seal relation. This results in Wearing away of the housing wall which is normally composed of a less wear-resistant material than is desired for cooperation with the radial periphery of the teeth. With this earlier construction when objectionable wear has taken place, the entire pump is considered expendable and is discarded.' Furthermore, with this earlier construction it wl be appreciated that the maximum area obtainable on the outer or back face of the radial bushing flange for the purpose of pressure loading the same is controlled by the radial thickness of the wall of the tubular liner portion surrounding the gear journal. Y .Y .Y 'Y

It is an object of the present invention to provide in a device of the present character, animproved arrangement of main body housing and an auxiliary liner assembly enclosing the fluid displacement member and having superior wearresistant characteristics to those of the main body housing and being readily replaceable thus eliminating the usual wasteful practice of considering the pump as expendable and discarding the entire structure when the same has become worn.

It is a further object to provide in an arrangement oi the above character, a replaceable wearresistant liner assembly particularly arranged to (Cl. 10S- 126) `facilitate the eiiective pressure .loading of the fluid displacement element, by increasing the area available for pressure loading.

Other objects, advantages and uses of my invention will become apparent from a reading of the following specification taken in connection with the appended drawing which forms a part thereof and wherein:

Figure 1 is an axial section view of a gear-type liquid pump incorporating a preferred embodiment of the present invention;

Figure 2 is a section view taken substantially on the line 2-2 of Figure 1;

Figure 3 is a perspective-like view of one of the bonnet-like bearing and pumping seal providing units forming the particular subject matter of the present invention; and l Figure 4 is an axial section view oi a pump incorporating an alternative embodiment of the present invention.

Referring now in greater detail to the particular forms shown in the drawing by way of example only, there is illustrated in Figure 1 a preferred embodiment of my invention. VA pump iii having a main pump housing assembly Il is composed preferably of a relatively light-weight material such as an aluminum alloy, which normally does not havethe most desirable wearresistant characteristics. Main housing I0 has an inlet i3, an outlet il, and an intermediate chamber ila for receiving a rotary fluid displacing unit l5. Received in substantially completely enclosing relation about the rotary displacement unit I5 is an auxiliary housing or wear-resistant liner assembly indicated generally at I6, the particular construction and arrangement of this,

liner assembly in combination forming the es'- sential subject matter of the present invention.

The main housing chamber Ila is preferably in the form of a pair of parallel intersecting 'cylindrical compartments or chambers, with the liner assembly I6 complementailly formed and received in enclosing relation above the fluid displacement unit l5 which is preferably in the form of a pair of gears, the teeth of which` lntermesh in the area of intersection of the parallel cylindrical chambers.

Each of the cylindrical chambers Ila have parallel radially extending end walls llb and llc and co-axially extending reduced bores Hd, the

gears proper being received in the chambers Ila.v

Each of the liner assemblies i6 comprises a first bonnet-like bearing and pumping sealQproviding unit referred to generally at I1 and a second closure liner unit indicated generally. at 2|.

the two units making up the complete liner assembly being composed of a wear-resistant material such as bronze and functioning to completely enclose the fluid displacing gears in bearing and fluid pumping seal relation.

The unit I1 includes a radially extending annular plate-like portion I8, a co-axially extending tubular liner I9 cooperating with theteeth of the corresponding gear in fluid pumping seal relation and terminating at I9a in spaced relation to the adjacent radial end wall I Ic providing for axial adjustment of the bonnet-like unit. A first radially extending bearing and pumping seal providing face 20 is formed on the inner side of radial flange I8 andan outer radially extending face I'Ia is normally spaced from the adjacent radially extending chamber wall IIb to provide therewith a pressure iiuid motive chamber for urging the bonnet-like unit axially to thus maintain said first inner face 20 in bearing and pumping seal relation to the adjacent gear side face. In addition unit II, in the more specific aspect of the present invention, includes a second tubular liner insert portion I9b embracing the corresponding gear journal and received within reduced bore I Id of the main housing II. Donut-type seal I9c is preferably included between tubular insert I9?) and the reduced cross-section bore IId. Alternatively the tolerance may be so closely maintained as to provide the necessary seal, particularly where the tubular portion I9b is given a suicient length. The enlarged tubular insert portion I9 is normally of sufficient length and the tolerance between this tubular portion and the surrounding housing is suiciently closely maintained to provide the requisite fluid seal, this being particularly true in view of the fact that tubular insert I9necessarily has an appreciable length considerably overlapping the embraced gear teeth.

The second closure insert unit 2| includes essentially a second radially extending annular plate 22 having a second radially extending inner face 23 defining a bearing and pumping seal surface with the corresponding side face of the gear and having -a second outer radially extending face 24 complementary to and engaging the corresponding radial end wall I Ic of the enclosing cylindrical chamber.

The radial outer periphery 22a of radial flange 22 is formed complementary to and is received within the outer terminal of enlarged tubular insert I 9 preferably in fluid sealed relation providing for axial adjustment of tubular bearing insert I9.

A passage 25- communicates at the inner terminal thereof with the gear teeth preferably at or adjacent the high pressure zone and communicates at the outer terminal thereof with the motive chamber deiined in part by the outer radial face I'Ia of radial flange 2li. It will be appreciated that passage 25 may be located so as to place the motive chamber in communication with the gear teeth at any arcuate position thereabout where-a positive pressure is generated. Plug 25a functions to prevent circulation of iiuid therepast between port I3, and the back of the bushings and the port I4. It will be readily appreciated that the pressure generated by the gear teeth ranges all the way from a slightly negative pressure in communication with inlet I3 to the maximum outlet pressure in communication with the outlet I4. Thus radial inner face 2li of radial t ange I 8 as well as the inner periphery of bearing insert tubular portion I9 are subjected to pressures ranging all the way from a slightly negative pressure at the arcuate position corresponding to inlet I3 to the maximum pressure at the arcuate position corresponding to outlet I4. On the other hand the pressure existing in the motive chamber in pressure actuating contact with radial outer faces IIa is uniform throughout the arcuate extent of this motive surface. Therefore there will exist a slightly dominating overbalance in the direction of the gear side face cooperating with radial inner face 20 of flange I8.

It is important to note that by virtue of the provision of tubular bearing insert`l9 the total radial dimension of iiange I8 is made greater than the radial dimension of the enclosed gear and hence radial outer face I'Iafunctioning as the motivating area is given an increased over-all area corresponding to the radial thickness of tubular insert I9.

Main outside body housing II is preferably formed in two parts including main portion IIe and closure plate portion IIf held together by means of cap screws I I g. It will thus be apparent that upon objectionable wear occurring in the bushing liner assembly I6, it is only necessary to remove cap screws IIg and separate the main portion IIe from the plate portion I If in order to readily replace both bearing and seal defining units I1 and 2I, thus preserving main body housing II for indefinite use.

Turning now to the modification shown in Fig. 4, it will be seen that this modification differs from that of the previous figures only in the additional provision of pressure relief means between the gear side faces and the corresponding annular plates, this relief being employed for the purpose of more eifectively accomplishing the required precise over-balance of the flange in the direction of the corresponding gear faces. It may be found in certain instances that the increased area of the motivating outer radial surface II'Ia of the flange II8, by virtue of the addition of axially extending tubular insert II9 embracing the gear teeth, is not sufficient to give the necessary overbalance in the direction of the gear face. This might be true where tubular portion II9b is given an increased radial thickness in proportion to the radial dimension of plate H8.

It will be observed that Fig. 4 is largely a sche-I matic showing, only one gear being shown, but it being understood that two gears will be employed in the same manner as in Fig. 1, the second gear having been eliminated for the purpose of simplicity. In Fig. 4 a liquid pump indicated generally at IIO comprises a main body housing-I Il containing a pair of adjoining substantiallycylindrical chambers iIIa, only one of which is illustrated, the arrangement being substantially identical to that of Fig. l. Each of the chambers Illa have radial end walls IIib, and. IIIc. Communicating with the chambers IIIa are inlet H3 and outlet II4. Received within chambers Ilia are two gear members H5 (only one being shown). these gear members meshing at the junction of the housing members in the manner shown in .bly H6 including a first bonnet-like bearing and pumping seal unit III and a second closer liner atrasos unit I2 I. The nrst bonnet-like bearing and pumping seal unit II'I comprises a first tubular liner portion IlBb surrounding the corresponding gear journal and received in the adjacent reduced co-axial bore. A substantially annular radial extending plate Il! is located at the inner terminal oi the first tubular liner portion and is received in the corresponding housing chamber Illa with a rst outer or back face Illa normally spaced from the adjacent end wall IIIb of the housing chamber and forming therewith a motivating pressure chamber for the reception of liquid underv pressure eiective to actuate said annular plate i8 toward the associated side face of the corre--v sponding gear. For the purpose of increasing the wear life of the pump as well as adding to the total effective pressureresponsive area ||1a with reference to the opposed area of the inner seal and bearing face |20, I have provided a second enlarged axially extending tubular insert Il! complementary in inner peripheral diameter to the gear teeth and corresponding in outer diameter to the receiving outer chamber. The axial terminal I |9a of this tubular insert is spaced from the adjacent end wall I Ic of the housing to provide for axial adjustment of the bonnet-like insert unit ill.

The second bearing and pumping seal unit |2| comprises a second radially extending annular plate i22 having a second back face |24 in ensagement with the adjacent radial wall of the corresponding chamber and a second radially ex tending inner face |23 engaging in bearing and pumping seal relation with the radial side :lace of the corresponding gear. The radial outer periphery |22a of this second annular plate is preferably received in the open terminal of the second tubular liner Il! in liquid sealed relation. The tubular liner Ils is arranged for axial adjustment with reference to the embraced annular flange |22,

Pressure generated by gear unit ||5 is directed through passage |25 past ball check valve I25a to the 'motive chamber in pressure contact with radial outer face .Illa of iiange IIB and vis eiiective to overbalance nange I|8 in the direction of .bearingand pumping seal engagement with the corresponding gear side face. Donut seals Ilse are interposed between the journal bearing insert ||9b and the reduced cross-section coaxial bore IIId. A similar passage |26 and ball check valve |2811 places inlet passage H0 in communication with the motive chamber. the ball check valves I25a and |26a functioning to make the pump automatically reversible.

The important distinction between the present form of insert liner assembly IIB oi Fig. 4 and that of the preceding figures resides in the provision of pressure relieving means indicated generally at |40. This relieving arrangement resuits in a more precise and eiective overbalance of radial flange I|8 in the direction or the gear side face. Relief |40 preferably comprises the formation of an annular channel |4| readily machined or otherwise formed in the radial bearing and seal face |20 and positioned radially inwardly of the roots of thegear teeth. The exact size of this annular relief |4I' is best determined by the cut and try method. By removing successive increments and trying the result, it is readily possible to ascertain the exact amount of material to be removed and the optimum size of relief |4I. In addition to the provision of this annular reliei` it is important to place this relie! in communication with a -sione of pressure lower than that in communication with the motive chamber and I prefer to accomplish this by forming axially extending splines or passages |42 in the inner periphery or tubular portion IISb. Passage |42 Aleads to passage |43 and alternatively through passage I4'4 or |45 and corresponding ball check valves Illa and |45a to the zone of lower pressure depending upon the direction of rotation oi gear unit IIB.

It will thus appear that while for most installations the simple form of construction shown in Fig. 1 will suiiice, I have also provided the arrangement disclosed in Fig. 4 for eil'ecting a more precise overbalancing pressure differential in the direction oi! the gear iside face.

While I have disclosed my invention in connection with certain speciilc embodiments thereof, I intend that this be by way or example and not limitation, the scope of my invention being denned by the appended claims.

I claim: 1. In a liquid pump comprising: means de ilning a main outside body housing composed oi' a ilrst material and having a chamber therein,

an inlet leading into and an outlet leading from said chamber; means including a rotary liquid displacement member in said chamber eiectivev to draw liquid in said inlet and force the same out of said outlet; means defining a completely enclosing wear-resistant readily replaceable liner assembly received in said chamber in enclosing relation about said rotatable liquid displacement member, including a first bonnet-like bearing and pumping seal unit, said rst unit comprising a radially extending annular plate having a rst back face normally spaced from the adjacent end wall of said chamber forming therewith a motive pressure chamber for the reception of liquid under pressure for actuating said annular plate axially toward said rotary.

liquid displacement member, said rst unit further comprising an axially extending tubular liner portion embracing the outer radial periphexyof said rotary member, said tubular liner merging with the radial outer .portion of said rst annu'- lar plate and terminating at the opposite axial extremity thereof in spaced relation to the adjacent end wall of said chamber to provide for limited axial adjustment of said first unit, said radial annular plate also having a rst front face engageable in bearing and -pumping seal relation with said rotary liquid displacement member, a second bearing and pumping seal unitcomprising a second radially extending annular plate having a second back face in engagement with the adjacent wall of said chamber and a second inner face engageable in bearing and pumping seal relation with said rotary fluid displacement member; and means placing said motive chamber in communication with liquid pressure generated by said liquid displacement means for maintaining said rst inner face of said rst radial annular plate in bearing and pumping seal relation with said rotary displacement member and said rotary displacement member in turn in bearing and .pumping seal relation with said second inner chambers; coaxial bores in the end walls of said housing chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; means defining a gear enclosing wear-resistant readily replaceable liner assembly received in each of said chambers and bores aboutsaid gears and journals, each of said assemblies including a first bonnetlike bearing and pumping seal unit, said first unit comprising a rst tubular liner portion surrounding-the corresponding journal and received in said reduced bore, a substantially annular radially extending plate portion at the inner end of said first tubular liner portion received in the corresponding housing chamber, said rst annular plate having a rst back face normally spaced from the adjacent end wall of said chamber forming therewith a motive pressure chamber for liquid under pressure for actuating said annular plate toward the associated side face of said gear, a second axially extending tubular liner of larger diameter than said iirst tubular liner portion, said second tubular liner merging with the radial outer portion of said annular plate and terminating at the opposite axial extremity thereof in spaced relation to the adjacent radial end wall of said chamber to provide for limited axial adjustment of said first unit, the inner periphery of said tubular liner embracing the teeth of the associated gear in pumping seal relation, said first radial annular plate also having a first radially extending inner face engaged in bearing and pumping seal relation with the adjacent side face of said gear, a second bearing and pumping seal unit comprising a second radially extending annular plate having a second back face in engagement with the adjacent wall of said chamber and a second radially extending inner face engaged in bearing and pumping seal relation with the adjacent side face of the corresponding gear; and means placing said motive chamber in communication with a liquid pressure generated by said gears for maintaining the inner face of said rst radial annular Wall in bearing and pumping seal relation with the adjacent ,side face of said gear and the oppositey side face of said gear in bearing and pumping seal relation with said second radially extending inner face of said second radial annular plate.

3.' In a pressure loaded gear pump: means defining a main housing of a first composition formed with a pair of parallel intersecting cylindrical chambers, an inlet to one side of said inter- Y secting area and an outlet from the other side thereof, pairs of reduced coaxial bores in the opposed end wallsof said cylindrical chambers; means deining an auxiliary housing liner assembly of wear-resistant metal received in each of said chambers, each assembly including a first bonnet-like bearing and pumping seal unit having a first tubular neck liner portion received in the corresponding one of said reduced bores in sealed axially adjustable relation thereto, a first radial flange portion, the outer face of which is spaced from the adjacent end wall of the main housing to form an auxiliary motive pressure chamber, and a second enlarged tubular liner portion extending axially of the corresponding cylindrical chamber with the open lterminal thereof in spaced relation to the end wall of said chamber to provide for limited axial adjustment of said bonnet unit, a second closure bearing and pumping seal unit having a second tubular neck liner portion received in the reduced bore adjacent the open end of said enlarged tubular liner portion, a second radial flange portion received with the outer periphery in fluid sealed relation within said open end of said enlarged tubular portion; a pair of gears received in said enlarged tubular portions of said bonnet members in completely enclosed relation therein, means defining an inlet to and an outlet from said enlarged tubular members corresponding to said main housing inlet and outlets; and means placing said auxiliary pressure chambers in communication with liquid pressure generated by said gears for forcing the inner face of said first radial flange into -pumping seal relation with the corresponding gear side face.

4. In a liquid pump comprising means defining a main body housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; a toothed gear member received in each of said housing chambers, said gear members meshing at the juncture of said housing chambers; coaxial bores in the end walls of said housing chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the oppQSite sides thereof into said reduced bores; means defining a gear enclosing wear-resistant readily replaceable liner assembly one received in each of said chambers and bores about said gears and journals, each of said assemblies including a first bonnet-like bearing and pumping seal unit, said iirst unit comprising a first tubular liner portion surrounding the corresponding gear journal and received in said reduced bore, a rst substantially annular radially extending plate portion at the inner terminal of said rst tubular liner portion received in the corresponding housing chamber, said first annular plate portion having a first back face normally spaced from the adjacent end wall of the associated chamber forming therewith a motive pressure chamber for liquid under pressure for actuating said rst annular plate toward the associated side face of said gear, a second larger axially extending tubular liner, said second tubular liner merging with the radial outer portion of said first annular plate and terminating at the opposite axial extremity thereof in spaced relation to the adjacent radial end wall of said corresponding chamber to thus provide for limited axial adjustment of said ilrst unit in floating relation to the embraced gear, the external diameter of said enlarged tubular liner being complementary to the inner periphery of the associated chamber and the inner periphery thereof being complementary to the enclosed gear teeth embracing the same in pumping seal relation, said first radial annular plate also having a first radially extending inner face engaged in bearing and pumping seal relation with the adjacent side face of the associated gear, a second bearing and pumping sealv unit comprising a second radial extending annular plate having a second back 'face in engagement with the adjacent wall of the associated chamber and a second radially extending inner face engaged in bearing and pumping seal relation with the adjacent side face of the corresponding gear, the radial outer periphery of said second annular plate being received in the open terminal of said enlarged tubular liner providing for axial adjustment of said enlarged tubular liner in liquid sealed relation to said second radially extending annular plate; and means placing said motive chamber in communication-with a liquid pressure generated by said gears for maintaining the inner face of said first radial annular walls in bearing and pumping seal relation with the adjacent side face of the associated gear and the opposite side face of said gear in bearing and pumping seal relation with said second radially extending inner face of second radial annular plate.

5. In a pressure loaded liquid pump comprising: means defining a main body housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet vleading from said chambers; a toothed vgear member in each of said housing chambers, said gear members meshing at the juncture of 'said housing chambers; .coaxial bores in the end walls of said housing chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the opposite sides thereof into said reduced. bores; means defining a gear enclosing wear-resistant readily replaceable liner assembly received in each of said chambers and bores about said gears and journals, each of said assemblies including a ilrst bonnet-like bearing and pumping seal uni-t,

said rst unit comprising a rst tubular liner portionsurrounding the corresponding gear journal and received in said reduced bore, a substantially annular radially extending plate'portion .at the inner terminal of said first tubular liner portion received in the corresponding housing chamber, said first annular plate having a nrst back face normally spaced from the adjacent end wall of said chamber forming therewith a motive pressure chamber for liquid under pressure effective to actuate said annular plate toward the associated side face of the corresponding gear, means effective to increase the wear life of the pump and increase the total effective pressure responsive area of said rst annular plate back face with reference to the area of the corresponding gear side face, said last named means including a second axially extending tubular liner of larger diameter than said first tubular liner portion. said second tubular liner merging with the radial outer portion of said annular plate and terminating at the opposite axial extremity thereof in spaced relation to the adjacent radial end wall of said chamber to provide for limited axial adjustment of said first unit, the inner periphery of said enlarged tubular liner embracing the gear teeth of the associated gear in pumping seal relation 'and the outer periphery of said enlarged tubular liner being complementary in diameter to the enclosing chamber and functioning as an elongated liquid seal therewith, said first radial annular plate also having a iiist radially extending face engaged in bearing and pumping sealing relation with the adjacent side face of said gear,

a second bearing and pumping seal unit comprising a second radially extending annular plate having a second .back face in engagement with the adjacent wall of said chamber and a second radially extending inner face engaged in bearing and pumping seal relation with the adjacent side face of the corresponding gear, the radial outer periphery of said second annular plate receiving the open terminal of said second tubular liner inA liquid sealed axially adjustable relation thereabout; and means placing said motive chamber in communication with a liquid pressure generated by said gears for maintaining the inner face of said ilrst radial annular wall in bearingv and pumping seal relation with the adjacent side 75 '10 face of said gear and theopposite side face of said gear in bearing and pumping seal relation with said second radially extending inner face of said second radial annular'plate.

6. In a pressure loaded liquid pump comprising: means deiining a main body housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having aninlet leading to and an outlet leading from said chamber; a toothed gear member in each of said housing chambers, s'aid gear Amembers meshing at the juncture of said housing chambers: coaxial bores in the end walls of said housing chambers vforming reduced extensions of said housing chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; means dening a gear enclosing wear-resistant readily replaceable liner assembly received in each of said chambers and bores about said gears and journals, each of said assemblies including a first bonnet-like bearing and pumping seal unit, said first unit comprising a first tubular liner portion surrounding the corresponding gear journal and received in said reduced bore, a iirst substantially annular radially extending plate portion at the inner terminal of said first tubular liner portion received in the corresponding housing chamber, said iirst annular plate having a first back face normally spaced from the adjacent e'nd wall of said chamber forming therewith a motive pressure chamber for liquid under pressure effective to actuate said annular plate toward the associated side face of the corresponding gear, means eiective to increase the wear life of the pump and increase the total eective pressure responsive area of said rst annular plate back face with reference to the area of the corresponding gear side face, said last named means including a second axially extending tubular liner of larger diameter than said nrst tubular liner portion, said second tubular liner merging with the radial outer-.portion of said annular plate and terminating at the opposite axial extremity thereof in spaced. relation to the adjacent radial end wall of said chamber tol provide for limited axial adjustment of said iirst unit, the inner periphery of said enlarged tubular liner embracingthe gear teeth of the associated gear in pumping seal relation and the outer periphery of said enlarged tubular liner being complementary in diameter to the corres'ponding chamber receiving the same and functioning as an elongated liquid seal therewith, said first radial annular plate also having a rst radially extending inner face engaged in bearing and pumping seal relation with the adjacent side face of the corresponding gear, a second bearing and pumping seal unit comprising a second radially extending annular plate having a second back face in engagement with the adjacent radial wall of the corresponding chamber and a second radially extending inner face engaged in bearing and-pumping seal relation with the adjacent side face of the corresponding gear, the radial outer periphery of said second annular plate receiving the open terminal of said second tubular liner in liquid sealed axially adjustable relation thereabout; means placing said motive chamber in communication with a liquid pressure generated by said gears for maintaining the inner face of said iirst radial annular wall in bearing and pumping seal relation with the adjacent side face of said gear and the opposite side face of said gear in bearing and pumping seal relation with said second radially extending inner face of said ll second radial annular plate and means defining .a relief recess between the gear side face and said iirst radial inner face of said first annular plate and means for placing the same in communication with a zone of lower pressure than that generated by said gears.

7. In a pressure loaded liquid pump comprising: means defining a main body housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers; coaxial bores in the end walls of said housing chambers forming reduced extension of said housing chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; means defining a gear enclosing wear-resistant readily replaceable liner assembly received in each of said chambers and bores about said gears and journals, each of said assemblies including a rst bonnet-like bearing and pumping seal unit, said first unit comprising a first tubular liner portion surrounding the corresponding gear journal and received in said reduced bore, a substantially annular radially extending plate portion at the inner terminal of said first tubular liner portion received in the corresponding housing chamber, said first annular plate having a first back face normally spaced from the adjacent end walls of said chamber forming therewith a motive pressure chamber for liquid under pressure effective to actuate said annular plate toward the associated side face of the corresponding gear, means effective to increase the wear life of the pump and increase the total effective pressure responsive area of said rst annular plate back face with reference to the area of the corresponding gear side face, said last named means including a second axially extending 'tubular liner of larger diameter than said first tubular liner portion, said second tubular liner merging with the radial outer portion of said annular plate and terminating at the opposite axial extremity thereof in spaced relation to the adjacent radial end wall of said chamber to provide for limited axial adjustment enlarged tubular liner embracing the gear teeth of the associated gear in pumping seal relation and the outer periphery of said enlarged tubular liner. being4 complementary in diameter to the enclosing chamber and functioning as an elongated liquid seal therewith, said first radial annular plate also having a first radially extending inner face engaged in bearing and pumping sealing relation with the adjacent side face of said gear, a second bearing and pumping seal unit comprising a second radially extending annular plate having a second back face in engagement with the adjacent wall of said chamber and a second radially extending inner face engaged in bearing and pumping seal relation with the adja-l cent side face of 4the corresponding gear, the radial outer periphery of said second annular plate receiving the open terminal of said second tubular liner in liquid sealed axially adjustable relation thereabout; means placing said motive chamber in communication with a liquid pressure generated by said gears for maintaining the inner face of said first radial annular wall in bearing and pumping seal relation with the adjacent side face of said gear and the opposite side face of said gear in bearing and pumping seal relationwith said second radiallyextending inner face of said second radial annular plate, a relief recess formed in said first inner radial face cf said rst annular plate located radially inwardly of the roots of the gear teeth and means placing said relief recess in communication with a zone of lower pressure than that generated by said gears.

v JOHN A. LAUCK.

REFERENCES CITED 4 The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,927,395 Edwards Sept. 19, 1933 2,202,912 Johnson June 4, 1940 2,345,975 Herman Apr. 4, -1944 2,346,761 Johnson Apr. 18, 1944 2,395,824 Herman Mar. 5, 1946 2,412,588 Lauck Dec. 17, 1946 

